The invention relates to a spinneret assembly and to a method for producing filaments.
Filaments of various polymeric materials such as for example, polyolefins, polyamides, polyesters, etc., are produced by feeding the polymer, which is solid and in particulate form, to a screw extruder in which the polymer is melted and extruded through a spinneret. A spinneret is essentially a plate having a plurality of orifices therein. The orifices form the molten polymer into filaments which are then cooled or quenched by a cooling medium, generally conditioned air, and then further processed as known in the art. In order to produce high quality textile products from synthetic filaments, it is important that the spinning process produce synthetic filaments having a high degree of uniformity. The present invention is primarily directed toward improving the uniformity of filaments produced by such spinning processes as previously described.
It has been suggested that one of the most significant factors contributing to filament nonuniformity during the spinning process is the fact that the temperature of the molten polymer passing through the orifices positioned near the center of the spinneret is higher as compared to the temperature of the molten polymer passing through the orifices positioned near the edge of the spinneret. The higher the temperature of the polymer the lower the viscosity and the lower the viscosity the faster the polymer under a given pressure passes through an orifice of the spinneret. Therefore, because of the temperature differential across the face of the spinneret, the flow rate of the molten polymer through the orifices of the spinneret varies which results in filament nonuniformity. Although attempts have been made to reduce the temperature differential across the face of the spinneret and thus improve the nonuniformity of the filaments, nonuniformity is still a problem.
An object of the present invention is to reduce the temperature differential across the face of spinneret, that is, the variation in the temperature of the filaments at the spinneret face beginning from the center of the spinneret and working radially outward.
Another object of the present invention is to extrude a molten polymer through a plurality of orifices simultaneously and at the same flow rate.
Still another object of the invention is to reduce the nonuniformity of filaments produced by melt spinning.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art upon studying the specification, drawings and the appended claims.